Identification of Schistosoma japonicum GSK3β interacting partners by yeast two-hybrid screening and its role in parasite survival

Schistosoma is the causative agent of schistosomiasis, a common infectious disease distributed worldwide. Our previous phosphoproteomic analysis suggested that glycogen synthase kinase 3 (GSK3), a conserved protein kinase in eukaryotes, is likely involved in protein phosphorylation of Schistosoma japonicum. Here, we aimed to identify the interacting partners of S. japonicum GSK3 beta (SjGSK3 beta) and to evaluate its role in parasite survival. Toward these ends, we determined the transcription levels of SjGSK3 beta at different developmental stages and identified its interacting partners of SjGSK3 beta by screening a yeast two-hybrid S. japonicum cDNA library. We further used RNA interference (RNAi) to inhibit the expression of SjGSK3 beta in adult worms in vitro and examined the resultant changes in transcription of its putative interacting proteins and in worm viability compared with those of control worms. Reverse transcription-quantitative polymerase chain analysis indicated that SjGSK3 beta is expressed throughout the life cycle of S. japonicum, with higher expression levels detected in the eggs and relatively higher expression level found in male worms than in female worms. By screening the yeast two-hybrid library, eight proteins were identified as potentially interacting with SjGSK3 beta including cell division cycle 37 homolog (Cdc37), 14-3-3 protein, tegument antigen (I(H)A), V-ATPase proteolipid subunit, myosin alkali light chain 1, and three proteins without recognized functional domains. In addition, SjGSK3 beta RNAi reduced the SjGSK3 beta gene transcript level, leading to a significant decrease in kinase activity, cell viability, and worm survival. Collectively, these findings suggested that SjGSK3 beta may interact with its partner proteins to influence worm survival by regulating kinase activity.